Schurr etal
rolling mill control



June 8, 1965 C, A, SCHURR ETAL Re. 25,795

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I-IORIzoNTAL VERTICAL ROLL SHAFT J ROLL SHAFT ENCODER ENCODER INVENTOR.

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June 8, 1955 c. A. scHURR ETAL Re. 25,795

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June 8, 1965 C, A, sCHURR ETAL Re. 25,795

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June 8, 1965 c. A. scHURR ETAL Re 25,795

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CONTROLLER Fi 5 INVENTOR.

United States Patent Olice Re. 25,795 Reissued June 8, 1965 25,795 ROLLING MILL CONTROL Charles Allan Schurr, Warrensville Heights, and Frank Alan Manners, Cleveland, Ohio, by Square D Company,

Detroit, Mich., a corporation of Michigan, assignee Original No. 3,104,566, dated Sept. 24, 1963, Ser. No.

767,712, Oct. 16, 1958. Application for reissue Oct.

14, 1964, Ser. No. 419,261

4 Claims. (Cl. 72-12) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The present invention relates to a control system for a rolling mill, and to the parts thereof, and more particularly t=o a control ysystem which establishes a rollin-g pattern in accordance with the conditions of a workpiece to be rolled and -then automatically causes the mill to perform a sequence of operations to reduce the workpiece from an origina-l thickness and width Ito a vfinal thickness and width .in accord-ance with the established pattern.

In the past, various attempts have been made to provide controls for various parts of a rolling mill. For example, screwdown positional devices under the contro-l of an operator `at a remote position have been devised for spacing the rolls for each successive pass and in accordance with a desired draft .as determined by the operator. Likewise, the operation of the entry and delivery tables, approach tables, side guides, horizontal and vertical rolls and other parts of the rolling mill have been remotely controlled by an operator so that the operator could cause the various parts of Ithe rolling mill to run in a desired sequence of operation and at desired speeds during the rolling of a workpiece.

It is well recognized in the industry that only operators of extremely high skill and long experience have been able to operate Ia rolling mill at optimum eiciency while obtaining final products of high quality. This was because every workpiece which went through the rolling mill was slightly different from every other workpiece and only a highly skilled operator was able to judge the number of passes or times the worpiece [is] was to be passed between the rolls, the draft of each pass, and other workpiece conditions which go together to make up a rolling pattern for that workpiece. Once the workpiece reached the approach and entry table of a rolling mill, it took a skilled .operator to mentally estimate the rolling pattern which he should luse and then complete the rolling operation in accordance with that pattern and while the workpiece was in rollable condition. This lwas particularly true of hot roll operations wherein the workpiece was rolled while it was hot. In order to operate the mill properly, the operator had to rst determine his rolling pattern. vEvery time there was a change in the dimensions, metallurgy, or temperature of the Workpieces being rolled, the operator had to select or determine .a new rolling pattern. Over a series of workpieces, it was often necessary for the operator to determine as many as several hundred new patterns, often one for each workpiece when there was no succeeding identical [worpieces] workpiece being rolled. It was very ditiicult even for a skilled operator, to mentally determine which of the several hundred patterns he should use for a workpiece which he saw for the iirst time when it reached the approach table. Very often, the operator misjudged the condition of the workpiece and had to change his rolling pattern after he had once started the rolling operation to prevent damaging the mill.

Furthermore, in the prior remote control systems, it was necessary for the operators to initiate and control the operation of all operable parts of the mill. This meant controlling the screwdowns of both vertical and horizontal rolls, controlling the direction and speed of rotation of all rolls, the direction and speed of rotation of the approach, entry and delivery tables, controlling the movement of the side guides, and any other operating parts o-f the mill. In addition to controlling each part, all parts had to be run in a co-operati-ve synchronized manner with the operator carefully watching to see that he was not overloading the mill and was obtaining optimum efliciency and output of a nal product of good quality. In most instances, it took the co-ordinated efforts of at least two operators working in timed relationship to control the mill.

In these prior attempts to control a mill, eachnew control added to the mill was devised to eliminate one particular function which the operator had to accomplish so that the operator could concentrate his attention on the remaining aspects of operation of the rolling mill.

In one instance, slippage of the vertical rolls on the workpiece was reduced by a control which fixed the speed of the vertical rolls to a denite proportion of the speed of the horizontal rolls. In another instance, the rolling pattern was Worked out in advance and recorded in such manner that the record could later be used to control the screwdown and other operations of the rolling mill, thereby improving the overall efficiency of the mill, provided the workpiece to be rolled arrived at the mill with conditions the same as the recorded conditions. It the records and workpieces were mixed, or if the workpieces did not arrive at the mill with their conditions exactly as previously recorded, the operator, would have to recognize these facts and alter the recorded p-attern suiciently to compensate for the deviations in actual and recorded workpiece conditions. -In other instances the mill was provided with controls which would reverse the entry and delivery tables after the workpiece passed through the rolls in one direction.

It is apparent that in all of these prior attempts of controlling a rolling mill, to increase its eiliciency, to reduce the possible damaging of the mill through misjudgement by the operator, and to increase the quality of the nal product, the overall control of a rolling mill in accordance with the conditions of a workpiece being rolled remained a problem. Also the determination of the rolling pattern, including the number of passes to be taken at the draft for each pass, [were] was often left entirely to the judgement of the operator at the time of rolling the workpiece.

One of the main objects of the present invention is to overcome the aforementioned deiiciencies in, and problems encountered with, prior control systems for rolling mills.

Another object of the present invention is to provide a control system which will automatically operate a rolling mill throughout a complete cycle of operation to reduce a workpiece from an original thickness to a desired iinal thickness.

Another object o-f the present invention is to provide a control system for a rolling mill which will increase the eiiiciency and life of a rolling mill, reduce the maintenance thereof, and increase the quality of the nal products of the mill.

Another object of the present invention is to provide a complete control system for a rolling mill, which includes determination of the number of passes a workpiece is to be sent through the mill, the draft for each pass, and the integration therewith of controls for vertical and horizontal rolls, entry and delivery tables, side guides and other operative parts of the mill.

Another object of the present invention is to provide a control system to establish a rolling pattern from the conditions of the workpiece to be rolled and to control the operation of a rolling mill in accordance with the pattern thus established.

Another object of the invention is to provide a control system for determination of the number ot times a workpiece is to be passed through a rolling mill to reduce the workpiece from an original thickness to a nal thickness, the number of passes being derived from the conditions of the workpiece at the starting of the rolling operation.

A further object of the invention is to provide a system for determination of the draft during each pass of a workpiece between the rolls of a rolling mill and for control of the screwdown in accordance with the draft determinations.

A further object of the invention is to provide a system for control of the relative speeds of the vertical rolls and the horizontal rolls during a particular pass in accordance with the draft during that pass.

A still further object of the invention is to provide a finished product formed by rolling a workpiece in a rolling mill controlled by a control system incorporating the features of the present invention as hereinafter claimed.

Other objects and a fuller understanding of the invention will become apparent from the claims and the following description of an embodiment of the invention taken in conjunction with the attached drawings in which:

FIGURE 1 is a plan view of a rolling mill controlled bythe present control system;

FIGURE 2 is a representative graph of a rolling pattern showing the reduction in thickness during each pass for a product which will be iinished in a succeeding rolling operation;

FIGURE 3 is a representative graph of a rolling pattern showing the reduction in thickness during each pass for a product which will not be further rolled;

FIGURE 4 is a block diagram schematic of the control system for the rolling mill shown in FIGURE 1;

FIGURE 5 illustrates an alternate structure for providing workpiece condition signals used in the control system illustrated in FIGURE 4;

FIGURES 6 and 6A when combined [is] form a chart showing the sequence of operation of the rolling mill in FIGURE l and as controlled by the system of FIGURE 4 for three passes;

FIGURE 7 is a block diagram schematic illustrating certain computing and positioning units used in the control system of FIGURE 4;

FIGURE 8 is a block diagram schematic illustrating the [number of passes computer] number of passes computer part of the control system of FIGURE 4;

FIGURE 9 is a block diagram schematic illustrating the horizontal total draft computer part of the control system of FIGURE 4; f

FIGURE 1() is a schematic wiring diagram illustrating the horizontal rolling pattern computer part of the control systern of FIGURE 4;

FIGURE l1 is a block diagram schematic illustrating the horizontal screwdown position control unit part of the control system of FIGURE 4 which spaces the horizontal rolls for each pass.

FIGURE 12 is a block diagram schematic illustrating the side guide positioner part of the control system of FIGURE 4;

FIGURE 13 is a block diagram schematic illustrating the draft compensation computer part of the control systern of FIGURE 4, which establishes the speed ratios of the vertical and horizontal rolls;

FIGURE 13A is an expanded circuit diagram of a part of FIGURE 13;

FIGURE 14 is a block diagram schematic illustrating the vertical total draft computer part of the control systern of FIGURE 4;

FIGURE 15 is a block diagram schematic illustrating the vertical rolling pattern computer part of the control system of FIGURE 4;

FIGURE 16 is a block diagram schematic illustrating the vertical screwdown position control unit part of the control system of FIGURE 4, which spaces the vertical rolls for certain passes.

An embodiment of the rolling mill control incorporating the features of the present invention is illustrated in the drawings for the purposes of exemplication and not for the purposes of limitation. Also, insofar as possible, schematic and block diagram type illustrations have been used to better point out the features of the present invention without detailing specic examples of components which are well known in the eld.

Referring to the drawings, there is illustrated in the plan View of FIGURE l a rolling mill having an approach table 1t), an entry table 11, and a delivery table 12 positioned to support a slab or workpiece 13 while it is being rolled by vertical rolls 14-14 and horizontal rolls 15. The terms slab and workpiece as used herein are meant to include any item capable of being worked on by spaced rolls or other tools between which the item is moved. The approach table 10 is driven by a suitable approach drive 16, which usually includes a variable speed electric motor interconnected wit-l1 the approach table 10 by a suitable driving mechanism illustrated by [the dash-dot] a dash-dor Zine 17. Similarly, the entry table 11 is driven by a suitable entry drive 18, which usually includes a variable speed electric motor interconnected with the entry table 11 by a suitable mechanism illustrated herein by [the dash-dot lines] a dash-dot line 19. Likewise the delivery table is driven by a delivery drive 20, usually including a variable speed electric motor mechanically interconnected with the delivery table 12 by a suitable mechanism represented herein by the dash-dot line 21.

The vertical rolls 14 and 14' are driven by a variable speed vertical roll drive 22 and are spaced apart by a vertical screwdown drive 23, both of which are connected to the rolls by suitable mechanisms, illustrated herein by [the] respective dash-dot lines 24 and 25. In the present instance, the vertical rolls 14 and 14 are illustrated and will be described as being on the entry table side of the main or horizontal rolls 15. It is understood however, that in some instances, 'the vertical rolls 14 and 14 may be positioned on the delivery table side of the horizontal [roll] rolls 15, and that such positioning of the vertical rolls 14-14 on the delivery side of 'the horizontal rolls 15 will necessitate certain minor changes in the herein described control system, but without departing 'from `the invention as hereinafter claimed.

As also illustrated in FIGURE 1, the horizontal rolls 15 are driven by a suitable variable speed horizontal roll drive 26, as for example, variable speed electric motors, and are positioned or spaced apart by a horizontal screwdown drive 27. The horizontal roll drive 26 and the horizontal screwdown drive 27 are suitably and mechanically interconnected with the rolls 15 by suitable interconnection means, illustrated herein by [the respective dash-dot lines 2S and 29. As also illustrated, the horizontal rolls 15 are rotatably supported by a mill housing 30 which must be suiiciently strong to withstand the forces exerted thereon by the rolls during the rolling operation. The details of construction of the housing 30 and various drives have not been illustrated herein, since these parts are commonly used in industry and are well known in the rolling mill industry.

The rolling mill also includes entry side guides 31 and 31' and delivery side guides 32 and 32 L] which are positioned on opposite sides of the horizontal and vertical rolls 15 and 14 and above their respective entry and delivery tables 11 and 12. The entry side guides 31 and 31' are moved towards and away from each other in directions transversely of the path of movement of a workpiece 13 through the horizontal and vertical rolls 15 and 14 'oy an entry side guide positioner 33, connecte-d to the entry side guides 31 and 31 by a suitable mechanism [J represented herein by [the dash-dot lines] a dash-dot line 34. Similarly, the delivery side guides are movable towards and away from each other in directions transversely of the path of movement of a workpiece 13 through the horizontal and vertical rolls 15 and 14 by a delivery side guide positioner 35, which is connected to the side guides 32 and 32 by a suitable meo'hanism[,] represented herein .by [the] a dash-dot line 26. The side guide positioners 33 and 35 are operative to move the respective side guides 31-31 and 32-32 towards each other to position the workpiece in the middle of the respective table 11 or 12 just before it enters the rolls and to [line] align the workpiece lengthwise of the entry and delivery tables 11 and 12.

WORKPIECE CONDITIONS For purposes of description, the workpiece 13 has a lead or leading end 37 vand a tail or trailing end 38. The workpiece also has condition-s representing various physical properties thereof. One of the conditions of the workpiece is the average original Ithickness condition, represented herein by the letter T0. Another condition is the average original width condition, represented herein by the letter 130. Another condition of the workpiece 13 is its original metallurgical condi-tion, for example, as evidenced by hardness, represented herein by the letter A." The original workpiece temperature condition is represented herein by the letter G. Along with these conditions, the desired final product conditions including final width Ef, final thickness Tf, and product designation B, as explained below, must also be known before a rolling pattern can be determined for the workpiece. With this information, a rolling pattern for the workpiece 13 to be rolled .is ascertained so that the desired final product will be produced by a rolling mill controlled by a control system incorporating the features of the present invention.

The final product of a rolling mill such as the one described herein may be either rough strip, wherein its thickness or surface quality need not be within very close tolerances, or finish strip, wherein close tolerances in thickness and surface finish must be maintained. Before a proper rolling pattern may be ascertained for a workpiece, it is, of course, necessary to know which of the aforesaid two types of final product is desired. One factor -to be considered in the determination of the correct rolling pattern for any workpiece is the nal product desired, for example, one of the choices above. This factor is herein referred to as the product design-ation B. If the required final product is designated as rough strip, one of two possible product designations B, wherein its thickness or [surfaces] surface finish does not have to -be Within very exact tolerances, a rolling pattern 40 such as illustrated in FIGURE 2 is generally used. The rolling pattern 40 of FIGURE 2 shows the reduction in thickness from an original thickness To to a final thickness Tf for a multi-pass operation wherein the workpiece is passed through the rolls and reduced in thickness. The draft or reduction in thickness of the workpiece 13 during the first pass is represented by the portion 41, the reduction in thickness during the final pass is represented by the portion 42, and the reduction in thickness for one of the intermediate passes is represented by the portion 43. The thickness of the workpiece at the completion of a particular pass will be referred to herein by the letter Tn wher-e n represents the numerical designation of the particular pass. It is noted that the draft, that is, the reduction in thickness during each pass is approximately equal to the draft for every other pass when rough final products are being rolled.

On the other hand, if the final product is designated as finish strip, the other of two possible product designations B, wherein close tolerances in thickness and sur-face [iinishes] finish are to be held, a rolling pattern 44 such as that illustrated in FIGURE 3 is usually used.

As may be seen `from this figure, if it is desired to obtain the final thickness and accurate surface conditions within very close tolerances, the draft for one pass is different than the draft for another pass. The reduction in -thickness during the first pass, represented by portion 45, is much greater than the reduction in thickness during the final pass, represented by the portion 46, s-o that the very fine finish tolerances can be obtained. The draft during one of the intermediate passes [are] is represented lby [p0rtions,] a portion such as portion 47.

Therefore, in the control system of the present invention, the determination of whether the final product is to be a finish strip -or a rough stri-p, the product designation B, is in operative effect va designation of one of two possible broad rolling patterns.

CONTROL SYSTEM The control .system for the rolling mill of FIGURE l is illustrated in block diagram in FIGURE 4. In this control system, the sequence of operations of the rolling mill, including `the approach table 10, entry table 11, delivery table 1l2, vertical rolls 14-14 horizontal rolls 15 and side guides 31-31' and 32-32' as well as the related dnives, positioners and screwdowns, is controlled by a master programmer 50. The solid lines in FIGURE 4 represent particular signals and related signal carriers or conductors for transmitting that signal, and the arows on the solid lines represent the direction of signal fiow. As illustrated, the master programmer 50 is connected by signal carriers 51, 52, 53- and 54 to position detectors PD1, PD2 and PD3 and a load detector LD1, respectively, which are mounted on or positioned in operative detection relation-ship with the rolling mill. The approach drive 16, entry drive 18, delivery drive 20, vertical .roll drive 22 and horizont-al roll drive 26 are directly controlled by respective controllers 57, 58, 59, 60 and 61, which 'are operated in accordance with signals or signal carriers 62, 63, 64, 65 and 66 interconnecting the respective controllers with the master programmer 50.

The control system also controls horizontal screwdown 27 by means of a horizontal screwdown controller 67, which is responsive to the signal in signal carrier 68 interconnecting horizontal roll digital control unit 69 with horizontal screwdown controller 67. Similarly, the ven tical screwdown 23 is controlled by a vertical screwdown controller 70, which is responsive to the signal in a signal carrier 71 interconnecting a vertical roll digital control unit 72 with vertical `screwdown controller 70. The horizontal roll digital control unit 69 and the vertical roll digital control unit 72 are responsive to the signals in respective signal carriers 73 and 74 interconnecting a screwdown program computer 75 with con-trol units 69 and 72 respectively as well as the signals in respective signal carriers 76 and 77, interconnecting the master programmer 50 with the control units 69 and 72 respectively. T-he signals from the master programmer 50 and. in signal carr-iers 76 and 77 cause the screwdowns to opn erate at the correct time during the sequence of operation of the mill and the signals from the screwdown progr-am computer 75 and in the signal carriers [76 and 77] 73 and 74 cause the screw downs to space the respective rolls at, the correct spacing or draft for each pass of the work piece 13 through the rolls 14 and 15. The horizontal roll digital control unit 69 is also responsive to the signal in a signal carrier 78 interconnecting a horizontal roll shaft encoder 79 and control unit 69 and to the signal in a signal carrier 80 interconnecting Ia horizontal calibration control 81 and the .control unit 69. Similarly, the vertical roll digital control `unit 72 is responsive to the signal in a signal carrier 82 interconnecting a [horizontal] vertical roll shaft encoder 83 with control unit 72 `and to the signal in .a signal carrier 84 interconnecting a vertical calibration control 85 with control unit 72.

As previously described, the Inill operates in accordance with the conditions of the workpiece 13. Thus, the control system must be provided with signals, each representing its respective condition of the workpiece 13. For purposes of clarity, the signal and its carrier or transmitting means will be referred to herein with the same reference character as the condi-tion per se. In FIGURE 4, the Sources for all condition signals [is] are represen-ted by a Isingle dash line block, herein referred to as condition signal sources 86, which is electrically interconnected with computer 7S to provide condi-tion signals to the screwdown program computer 75. The entry side guide positioners 33 and 35 are controlled by a side guide controller 87, which is responsive to the signal in a signal carrier 88 interconnecting condition signal sources 86 with side guide controller 87 as well as a signal in a signal carrier 89 interconnecting master programmer 50 with side guide controller 87. As will be more fully described later, signal carriers also connect the data translator and pyrometer portions of the condition signal sources 86 to screwdown program computer 75.

The inherent conditions such as thickness, temperature, metallurgy or resistance to rolling and other similar factors of workpiece 13 must be taken into consideration in determining the number of passes and the draft for each pass during the rolling operation. These various conditions are translated into electrical signals so that they may be combined or otherwise used by the control system. The condition signal sources 86 is the source of each of these condition signals and thus must include translators for converting condition information to electrical condition signals.

CONDITION SIGNAL SOURCES The information representing the conditions of original thickness To, desired final thickness Tf, original width En, desired linal width Ef, metallurgy A, desired final product designation B, and the temperature G of the workpiece 13 is converted into representative electrical signals by the data translator 90 portion of condition signal sources 86.

The conditions of original thickness TD, original width En, and metallurgy A are preferably obtained directly from the workpiece 13 while it is on the approach or entry tables and immediately prior to the rolling operation, thus eliminating possibility of human error in setting controls, or in selecting punch cards for the billets. As illustrated in FIGURE 5, these measurements or conditions of the workpiece 13 are obtained by a plurality 3f translators 86E, 86T, and 86A, which provide elec- :rical signals representing the original width, original :hickuess, and metallurgy, respectively. The electrical tignals derived by the translators 86E, 86T and 85A nay be considered as being portions of the data transator 9G. As an alternative the data translator 90 may 9e a card and card reader or a punched or magnetic tape 1nd tape reader, or other similar data translating means :ommonly used for the purpose of translating informa- :ion to electrical signals. The data supplied on the card )r tape reliects the existing condition of the billet, and :he selection of the rolling program is not made by the )perator but by the control system itself from the billet lata. When such equipment is used, the card or tape nust be fed into the data translator at the time the work- Jiece is to be rolled. The electrical signal representing he temperature condition G of the workpiece is easily :stablished by a pyrometer 91. The metallurgy of the vorkpiece might be established by a bounce test or simiar means to determine the hardness of the billet.

The structure and intricate mechanisms in the data ranslator and in the parts thereof are not described or llustrated in detail herein, since these details form no )art of the present invention and since various designs if data translators are available for converting workiece conditions into respective electrical signals.

The control system as illustrated in FIGURE 4 also ncludes a master control 92 electrically interconnected o the master programmer 50 by electrical connections 93 to control the starting and stopping of the control system. The master control 92 may be in the form of a pushbutton or other electrical device, which may be manually operated by a rolling mill operator to start the rolling mill or to stop it as desired.

MASTER PROGRAMMER As previously described, the master programmer 50 provides signals which control the sequence of operation of the various parts of the rolling mill, including the horizontal and vertical roll drives, the horizontal and vertical screwdowns, the approach, entry and delivery tables, and the entry and delivery side guides. For purposes of exemplitication and not of limitation, the sequence of operation for passing a workpiece 13 through the rolls three times is detailed in the chart of [FIGURE 6] FIGURES 6 and 6A.

Although the chart is for three pass operation, i.e., the workpiece is reduced in thickness in each of three successive passes of the workpiece through the rolls of the mill, it is understood that any number of passes may be used, dependent on the conditions and the rolling pattern established for a particular workpiece. In this particular chart, at least some of the conditions of the workpiece are recorded on a card for translation by a card reader type of data translator 90. Thus, in this instance when a workpiece 13 arrives on the approach table 10, a :card containing data for that workpiece 13 provides at least some of the conditions for the data translator 90. At this time, all parts of the mill are otf or de-energized and not operating.

Manual manipulation of the master control 92 initiates the operation of master programmer 5t) to operate the mill in accordance with the sequence of operations and the control system illustrated in FIGURE 4. When the master control 92 is operated, it causes the master programmer 50 to send a signal by means of signal carrier 62 to the approach table controller 57, which ultimately starts the approach table 10 running at an approach speed forward to move the workpiece 13 in the direction of right to left in FIGURE 1. Following this, the data translator and pyrometer 91 of signal sources 86 convert the workpiece conditions to electrical signals which are fed through signal carriers to the side guide controller 87 and screwdown program computer '75, As soon as the signals from the pyrometer 91 and the data translator 90 are made available by the condition signal sources 86, the screwdown program computer 75 responds to these signals and produces signals which are transmitted to the horizontal and vertical screwdown controllers 67 and 70, which control the screwdowns 27 and 23 of the horizontal and vertical rolls 15 and 14. Simultaneously, the master programmer signals the entry controller 58 to start the entry table moving at an approach speed forward, and also signals the side guide controller 87 to cause the side guides to operate to their odd pass position and move towards each other to position workpiece 13 in the middle of the entry table 11. When the leading end 37 of the workpiece 13 reaches the position detector PD3, a signal is transmitted by carrier 53 to the master programmer 50. The master programmer 5t) responds to the signal in carrier 53 and causes the approach table controller 57 and entry table controller 58 to stop the forward movement of the approach table 10 and the entry table 11. The side guides 31 are operative to center the workpiece on the entry table 11 and the horizontal and vertical screwdowns are operative to position the horizontal and vertical rolls 15 and 14 at the correct spacing for the iirst draft or first reduction in the thickness of the workpiece from its original thickness T,J to an intermediate thickness Tn. When the horizontal screwdown roll opening is within a preset distance from its programmed separation, the master programmer 50 signals the horizontal and vertical roll drive controllers 60 and 61 by means of respective signal carriers 65 and 66 and the entry table controller 58 by means of signal carrier 63, causing them to initiate forward movement of the rolls and 14 and the entry table 11 at an entry speed. If the screwdowns have not already properly spaced the rolls, they complete their operation while the roll drives and entry table are running at entry speed forward. The entry table 11 continues to move the workpiece 13 towards the rolls 15 and 14 until the leading end 37 of workpiece 13 is in the rolls 15 thereby operating the detector LDI, which then sends a signal by signal carrier 54 to the master programmer 50. This signal causes the master programmer 50 to [in turn] signal, in turn, the horizontal and vertical roll drive controllers 61 and 60, the entry table controller 58 and the delivery table controller 59 to operate the respective rolls and tables at rolling speed forward.

The horizontal and vertical rolls 15 and 14, the entry table 1-1 and the delivery table 1:2 continue their rotation in the forward direction until the tail end 38 of work- .piece 13 passes .the posi-tion detector PDI, causing the position detector PD1 to signal by means of signal carri-er 51 the master programmer 50 to that effect. At this time, the ho-rizontal and vertical screwdowns v27 and 23, .the approach table 10, and vside guides [33 and 34] 31-31 and 32-32 ar-e not moving. The horizontal and vertical roll drive controllers 60 and 61 now respond to the signals in carriers 65 and 66 from the master programmer 50 to cause the horizontal and vertical rol-ls 15 and 14 to run `at an exit sped forward. Simultaneously, the entry table controller 58 responds to the signal in signal carrier 63 from master programmer 50 and causes the entry table 11 to stop running. Also, simultaneously the delivery table controller 59 responds to the signal in signal carrier 64 from the master program-mer 50 and causes the delivery table drive to operate the delivery table 1,2 at an exit speed forward to move the workpiece from the 'rolls and in ,a direction from right to left in FIGURE l.

The workpiece is now arriving on the delivery table 12 from the rst pass through t-he rolling mill. The first reduction in thickness or rst draft causes the workpiece 13 to have a new thickness lherein referred to as thickness T1. When the workpiece 13 leaves the horizontal rol-ls 15, the detector LD1 responds to signa-l the master programmer 50 by means of signal carrier 54. The master programmer 50 in turn sends signals through signal car- .riers 65 and 66 to cause the horizontal and vertical roll drive controllers 60 and 61 to stopl rotation of the horizontal and vertical rolls 15 and 14. At this time and as soon as the workpiece l13 ha-s left the horizontal rolls 15, the horizontal and vertical roll digital control [unit] units 69 and 72 respond to the [signal] signals in signal carriers 76 and 74 from screwdown program computer 75 and the signals in signal carriers 76 and 77 from the master programmer 50 to establish the spacing of the rolls for .the next draft or pass. The horizontal and vertical screwdown controllers 67 and 70 respond to the digital contro-l units 69 and 72, respectively, to initiate movement of the horizontal and vertical screwdowns 27 and 23 to the correct rol-l spacing for the next pass or draft and as det-ermined by the rolling pattern previously established by the screwdown program computer 75. At this time, the horizontal and vertical rolls, the entry table, and the approach table are not running, as is indicated by the term OFF in FIGURES 6 and 6A. However, the delivery table cont-inues .running at the exit speed forward while the screwdown starts to yspace the horizontal and vertical ro-lls for the next pass of the workpiece therethrough, or if the rolling operation is completed, to move the workpiece away from the rolls so that the mill may be readied for the next workpiece.

Referring again to FIGURES 6 and 6A which illustrate a sequence of operation for three passes of the workpiece, it is noted that when the horizontal scr-ewdown reaches a position, a predetermined distance from it-s new spacing for the second draft or pass, the master programmer 50 signals the delivery table controller 59 to start rotation of the delivery table 12 in the reverse direction at an entry speed. Rotation of delivery table 12 in the reverse d-irection will move a workpiece there-on from left to right in FIGUREl l and towards the horizontal rolls 15. Simultaneously, the horizontal roll drive receives a signal from the master programmer 50 to star-t rotation of the horizontal rolls 15 at an entry speed in the reverse direction so that the workpiece 13 may be sent through the rolls 15 `and towards the entry table 11 and approach table 10 to again reduce the thickness Vof the workpiece. In this particular instance, the master programmer 50 signals the vertical roll drive controller 60 to keep the vertical roll drive olf and also signals the vertical screwdown controller to move the vertical rolls back away from the workpiece 13 while the workpiece 13 is passing through the horizontal rolls for the second pass.

The opera-tion as described in connection with the first pass is substantially repeated throughout the romain-ing passes until lthe workpiece 1:3 has been reduced to the desired tinal thickness.

SOREWDOWN COMPUTER Thus far, in the description, the function of the screwdown computer 75 land its association with the master programmer 50 and other parts of the control system have been described. The screwdown program computer 75 and other components which have been designed specifically -for the present control system will now be described in more detail.

A's described, one of the first steps in the rolling mill operati-on is to determine a rolling pattern, including the number of passes required, to reduce the workpiece 113 from its original thickness To to its desired inal thickness Tf and the draft for each pass. In the present control system, as illustrated in FIGURE 7, a number of pass-es computer 100 and a horizontal total draft computer 101 are provided. The screwdown program computer 75 also includes .a horizontal rol-ling pattern computer 102, a vertical rolling pattern computer 103, a vertical total dra-ft computer 104, and a draft compensation computer 105.

The horizontal draft computer 101 is electrically connected to the dat-a translator of signal sources 86 by the signal carriers 110 and 1111 to receive condition signais representing the original To and desired tinal Tf thickness respectively of the workpiece 13. The vertical total draft computer 104 is electrically connected to the data translator 90 of signal sources 86 by signal carriers 111-2 and 1113 to receive the condition signals representing the original ED and desired final Ef width respectively of the workpiece 13. rThe number of passes computer is connected to the pyrometer 9.1 of signal sources 8'6 by a signal carrier 114 to receive the temperature condition `signal G and is also connected to the data translator 90 by a signal carrier 115 to receive the metallurgy A and tinal product B signals.

The ver-tical total draft computer .104 subtracts the signal in signal carrier [112] 113 from the signal in carrier [113] 112 and provides, in a sl'gn'al carrier 119, `a resultant or combined signal [(Ef-Eo)] Eo-Ef which represents the increase in width of the workpiece 13 or the difference between the original width and desired fin-al width of the workpiece. Similarly, the horizontal total draft computer 101 subtracts the signal in carrier 111 from the signal in carrier 1.10 and provides a lresultant signal (T0- Tf) which represents the tot-al reduction in thickness or the difference between the original thickness and the des-ired -nal thickness of the workpiece. The vertical total draft computer 104 also provides, in a carrier 116, the original width signal Ea in analog form. 'Iihe vertical total draft computer 104 and the horizontal total draft computer 101 are each electrically connected to the number of passes computer 100 by a signal carrier 116 and 117, respectively, to transmit the [respective] resultant or cornbined Esignals] signal .(Tn-Tf) .and [Ef-EOE the signal Eo to th-e number of passes computer 100. The number of passes computer 160 responds to all o-f these signals G, A and B, [(Ef-Eo)] Eo and (TU-Tf) in signal carriers 1\1*4, .115, 116 and 117 respectively and determines the number of passes required to reduce the workpiece 13 from its Aorigin-al thickness To to the desired iinal thickness Tf without overloading the rolling mill or subjecting it to unnecessary or damaging stresses. Connected to the number of passes computer U is a signal carrier 1118 which transmits from computer 10d a signal representing the determined number of passes or times the workpiece is to be reduced in thickness by the horizontal rolls 1/5. This signal carrier effects `operation of the horizontal and vertical rolling pattern computers 102 and 193 as will later be described in more detail.

NUMBER OF PASSES COMPUTER As illustrated in FIGURE 8, the number of passes computer 160 includes a plurality of signal responsive devices such as relay coils or devices 12), 121, and 122, each of which is desivned to respond to its own individual signal as represented by lines 123, 124, and 125 respectively and not to respond to other signals. The electrical signal responsive devices 120, 121 and 122 are electrically connected through a pass determining circuit 126 and a suitable computing system including servo motors 127 and 12S, servo amplifiersr 129 and 130, potentiometers 131, 132 and 133, adder 134 and relay control 135. The potentiometer 131 is electrically connected by signal carrier 117 to the horizontal total draft computer 101 to receive the signal To-Tf, representing the diii'erence between the original thickness and desired final thickness signals from the condition signal sources 86. Potentiometer 132 is electrically connected to the vertical total draft computer 104 by signal carrier 116 to receive the original width signal Eo (in analog form) therefrom. Potentiometer 133 is electrically interconnected between the potentiometer 131 and the pass determining circuit 126 by signal carriers 136 and 137.

Signal carrier 137 is positioned along potentiometer 133 by servo motor 127. Servo motor 127 is responsive to the temperature signal G since it is connected by signal :arrier 138 to servo amplier 129 which receives its signal from pyrometer 91 by way of signal carrier 114. The signal carrier 136 is positioned along the potentiometer 131 by servo motor 128. Servo motor 128 is connected by signal carrier 139 to servo amplifier .130, which in turn is electrically connected to adder 134 by signal :arrier 140.

Interconnecting the potentiometer 132 and the adder 134 is a signal carrier 141, which is positioned along potentiometer 132 by relay control 13S. Adder 134 is also connected to relay control 135 by `a signal carrier [42 and relay control 13S is electrically connected to the signal carrier 115 to receive the metallurgy and final product condition signals A and B from the condition signal sources 86.

Signal ED representing the original width of the workpiece is fed into the potentiometer 132 by signal carrier 116 and signals A and B are fed into the relay control [35 by signal carrier 115. The relay control 135 coaperates with potentiometer 132 by positioning carrier l41 therealong to combine the original width and iinal sroduct signals E0 and B into an analog signal BEo which ls transmitted by the carrier 141 and also converts metallurgy signal A to analog form and directs signal A onto :arrier 142. The adder 134 then adds this combined signal BEo on carrier 141 to the signal A on carrier 142 io that a resultant analog signal (A-i-BEO) appears on :arrier 140. The servo amplier 130 amplies the signal (A-t-BEO) and carrier 139 transmits the amplied signal :o the servo motor 128, thus causing the servo motor 128 :o position carrier 136 along potentiometer 131 and in accordance with the signal (A-i-BEQ) on carrier 139.

CII

As previously described, the analog signal representing the difference in the original and iinal thickness (T0-Tf) is fed into potentiometer 131 by signal carrier 117. Servo motor 12S and potentiometer 131 eifectively multiply the two signals, i.e. the signals (A4-BEC) on carrier 139 and (T0-Tf) on carrier 117 so that the resultant analog signal (A+BE0)(T.-Tf) appears on signal carrier 136 and thus at the potentiometer 133. Servo motor 127 cooperates with the potentiometer 133 to effect a combination of the signals (A-l-BEMTo-Tf) on carrier and the signal G on carrier 13S into a final signal (A-i-BEO) (Tr-Tf) G, which signal is then fed through carrier 137 to the pass determining circuit 126 which may be in the form of a voltage magnitude switching system capable of causing operation of the desired one of devices 12d, 121, or 122. One example of such a device is a contact making voltmeter in which each set of contacts is open or closed, depending on the voltage impressed on the meter. Thus one of the signal responsive devices, for example relay coils 120, 121, or 122, operates or is energized in response to the magnitude of the output of the pass determining circuit 126.`

It is to be noted that the workpiece conditions heretofore explained, including To, Tf, ED, A, B and G, are represented by electrical signals. Consequently, their combination as recited in accordance with a formula for the determination of a discrete number of passes need not be dimensionally correct since the required unit conversion is inherent in the structure of the electrical apparatus described. A mathematically correct formula would include proper constants to make the equated quantities agreeable -as to units and would appear as follows: (AK1-lBE)(T0-Tf)GK2=No. of passes, where K1 and K2 are constants required to render the equation dimensionally correct.

In the present complete control system, the energization or operation of the signal responsive devices 121), 121 and 122 alfects the operation of the horizontal rolling pattern computer 102 in a manner which will later be described. It is apparent however, that the number of passes computer 100 operates in accordance with the invention and is herein described to provide a control system for determining the number of times or passes a workpiece is to be passed through the rolling mill to reduce the workpiece from an original thickness to a final thickness. The determined number of passes is derived from the conditions of the workpiece at the start of the rolling operation and the end product land final dimensions.

The original thickness, original width and metallurgy conditions may be alternatively measured directly from the workpiece by their respective signal source portions, diagrammatically illustrated as 86T, 86E, and 86A in FIG- URE 5 of the signal sources 86.

The number of passes is automatically and quickly obtained from the workpiece while it is on the approach table or the entry table. Thus the problem of estimating the number of passes from the conditions of the workpiece is removed from the operator so that he may more eiectively oversee other operations of the rolling mill. This also eliminates the possibility of overloading the mill housing or other parts of the mill.

HORIZONTAL TOTAL DRAFT COMPUTER The horizontal total draft computer 101 illustrated in FIGURE 9 includes digital to analog converters 145 and 146 and an analog subtract circuit 147. The digital to analog converter 145 is electrically connected by the carrier 11i) to the condition signal source 86 so that it will receive a digital signal T0 therefrom, which represents the original thickness condition of the workpiece 13. The digital to analog converter 146 is connected by carrier 111 to the condition signal source 86 so that it will receive a digital signal Tf therefrom representing the desired nal thickness of the final product. The digital to analog converters 145 and 146 simply convert the digital type of signal to an analog type of signal so that the signals To and Tf may be subtracted by the subtract circuit 147, which is electrically connected to both digital to analog converters 145 and 146 by signal carriers 148 and 149 respectively. The subtract circuit 147 is electrically connected to the number of passes computer 100 and the horizontal rolling pattern computer 102 by signal carrier 117 and provides an analog type signal (T0-Tf) representing the difference between the original and desired final thickness of the workpiece 13.

HORIZONTAL ROLLING PATTERN COMPUTER The horizontal rolling computer 102, as illustrated in FIGURE 10, has a rough strip final product bank 160 of voltage dividers or rheostats and a nish strip final product bank 161 of voltage dividers or rheostats. In the specific embodiment and for the purpose of exemplification and not of limitation, the rough strip final product bank 160 has a three pass voltage divider 162, a five pass voltage divider 163, and a seven pass voltage divider 164. Similarly, the finish strip final product bank 161 has a three pass voltage divider 165, five pass voltage divider 166 and a seven pass voltage divider 167.

Voltage divider rheostats 162, 163 and 164 are selectively connected to source 160 by electrical contacts 170, 171 and 172 respectively. Likewise, rheostats 165, 166 and 167 are selectively connected to source 161 by electrical contacts 173. 174 and 175. Sources 160" and 161 are selectively connected to supply 117 by electrical contacts 168 and 169. Contacts 168 and 169 are selectively operated by a final product signal from the data translator. Closing of the selected one of switches 168 or 169 determines which one of rheostat banks 160 or 161 will respond to the signal in carrier 117. If the contacts 168 are closed, condition signal (TO-Tf) representing the difference between the original thickness T and the final thickness Tf and appearing in carrier 117 energizes the selected one of the voltage dividers 162, 163 and 164, depending on which of these dividers is selected by the number of passes computer 100. The energization of a selected one of voltage dividers 162, 163, or 164 is controlled by inserting contacts 170, 171 and 172 in series in their respective leads 162', 163', and 164 and having those contacts 170, 171 and 172 operated by their respec* tive signal responsive devices on relay coils 120, 121 and 122 of the number of passes computer 100. Similarly, contacts 173, 174 and 175 are connected in series in the leads 165', 166 and 167 respectively and are also operated along the contacts 170, 171 and 172 by the signal responsive devices 120, 121 and 122 respectively.

As illustrated, each voltage divider has electrical output taps which divide the voltage across the voltage divider. Each tap includes a blocking rectifier. The blocl ing rectiers prevent circulation of the electrical output of any one tap through any other tap and also through any other voltage divider. Each tap and its respective blocking rectifier is identified in the drawing by a single reference character.

As an example, the voltage divider 164 of the rough strip final product bank 160 is divided into seven parts in accordance with the graph of FIGURE 2, and the voltage divider 167 of the finish strip nal product bank 161 is divided into seven parts in accordance with the graph in FIGURE 3. Blocking rectifier taps 157, 176, 177, 178, 179 and 180 at the ends of the voltage dividers 162, 163, 164, 165, 166, and 167 respectively are connected together by a conductor 181 to a position 182 on a selector switch 183, or stepping relay controlled by master programmer 50. The first draft or pass taps 184, 185, 186, 187, 188, and 189 of the voltage dividers 162, 163, 164, 165, 166, and 167 respectively are connected together by conductor 190 to a position 191 on selector switch 183 and to a position 192 on a selector switch 193, or stepping relay controlled by master programmer 50'.

14 The second draft taps 194, 195, 196, 197, 198, and 199 of the voltage dividers 162, 163, 164, 165, 166 and 167 respectively are connected together by conductor 200 to a position 201 on selector switch 183 and a position 202 on .selector switch 193. The third draft taps 203, 204, 205,

206, 207 and 208 of the voltage dividers 162, 163, 164, 165, 166 and 167 respectively are connected together by conductor 209 to a position 210 on selector switch 183 .and a position 211 on selector switch 193. The fourth draft taps 212, 213, 214, and 215 of the voltage dividers 163, 164, 166 and 167 respectively are connected together by conductor 216 to a position 217 on selector switch 183 and a position 218 on selector switch 193. The fifth draft taps 219, 220, 221 and 222 of the voltage dividers 163, 164, 166 and 167 respectively are connected together by conductor 223 to a position 224 on selector switch 183 and a position 225 on selector switch 193. The sixth draft taps 226 and 227 of the voltage dividers 164 and 167 respectively are connected together by conductor 228 to a position 229 on selector switch 183 and to a position 230 on selector switch 193. The seventh draft taps 231 and 232 of the voltage dividers 164 and 167 respectively are connected together by conductor 233 to a position 234 on selector switch 183 and to a position 235 on selector switch 193. The selector switches 183 and 193 have contact arms 236 and 237 respectively which are movable from one position to another. These arms move as the program advances from one pass to the next. Contact arm 236 is connected to a signal carrier 238 and con-V tact arm 237 is connected to a signal carrier 239.

HORIZONTAL SCREWDOWN DIGITAL CONTROL UNIT The horizontal roll digital control unit 69, calibration controls 81, shaft encoder 79 and horizontal screwdown controller 67 of the control system of FIGURE 4 are combined into and form a horizontal screwdown digital control unit 250, illustrated in block diagram in FIGURE 7 and in further detail in FIGURE ll. The horizontal screwdown 27 in FIGURE l includes a screwdown motor 251 which is rotated in opposite directions as directed by a screwdown controller 252, which is electrically connected thereto by connection 253.

The screwdown position control unit 250 receives signal Tf representing the desired nal thickness of the workpiece from the condition signal source by means of a signal carrier 111 which interconnects control unit [252] 250 and signal source 86, and a draft or pass signal (Tn-T1) from the horizontal rolling pattern computer 102 by means of signal carrier 239 which interconnects control unit [252] 250 and computer 102. These signals from carriers 111 and 239 are coordinated with `a feedback from the screwdown motor 251 to inform screwdown controller 252 how to control the screwdown motor 251 in a. manner now to be described.

As illustrated in FIGURE ll, the digital final thickness signal Tf is received from condition signal source 86 by signal carrier 111 electrically connected to a stop comparator and direction senser 254. Interconnected with direction senser 254 by means of connections 255 and 256 are a motor 257 and a shaft encoder 258 respectively. The motor 257 and the shaft encoder 258 are also interconnected mechanically by suitable means, for example, a gear box 259. The stop comparator and direction senser 254 causes the motor 257 to rotate towards a position as dictated by the signal Tf received from the signal carrier 111, and the shaft encoder 258 causes the motor 257 to stop when it has reached that position. Also, mechanically interconnected with the shaft encoder 258 L] and the motor 257 is a differential 260 having three shafts, namely, 261, 262 and 263. Shaft 261 is connected to the shaft encoder 258. Shaft 262 is connected to a shaft encoder 264, and the shaft 263 is connected to a servo motor 265 Which responds to a digital signal (Tn-Tf), received by means of signal carrier 239 from 

